Originally Posted by solipsism
No expertise? I'd think iTunes Store in and of itself qualifies Apple as an expertise in running services from the cloud.
That's why after the MobileMe team bungled their launch, the head of that group was demoted and was replaced by the person who ran the iTunes Store. More recently, Apple gave that person 100,000 Restricted Stock Units as a retention bonus. His name is Eddy Cue.
Eddy knows how to run cloud services and frankly, I wouldn't be surprised if he was the one who lobbied for multiple third-party services to help host iCloud.
Apple certainly has the financial resources to build and run everything themselves, however in reality, it's probably more reliable and safer to spread the load onto multiple service operators and domains. If a DDoS attack takes out Apple's servers, there are still AWS and Azure servers to shoulder the load.
Apple has been running their MobileMe mail service on big iron: Oracle/Sun. They know that certain scenarios call for outside partnerships (e.g., manufacturing), they aren't stupidly trying to do everything themselves like they did in the mid-Nineties.